Start with the 传感器, not the number of transmitter terminals
Pt100 identifies a platinum resistance 传感器 with a nominal resistance of 100 Ω at 0°C; it does not identify its lead-wire count. Texas 仪表' RTD guide describes the 传感器 characteristic and the different connection arrangements. An RFQ should therefore state both the 传感器 type and the wiring arrangement, together with the compatible transmitter input. This is a general technical explanation, not a declaration that every WESIVO 模块 supports all wire modes.
Two-wire measurement includes the lead path
In a conventional two-wire RTD connection, the resistance seen by the measuring circuit includes the 传感器 and both leads. A simple circuit example is R_seen = R_传感器 + R_lead1 + R_lead2. If an illustrative 传感器 is 100 Ω and each lead contributes 1 Ω, the circuit sees 102 Ω. This is an assumed resistance example, not a WESIVO test result. Converting that total directly as 传感器 resistance introduces a 温度 offset; adding display digits does not remove the lead contribution.
Three-wire compensation depends on the arrangement
DwyerOmega describes three-wire compensation and its assumption of comparable lead resistances. Unequal conductors or connection resistances can leave a residual error. For procurement, request the transmitter's terminal drawing and allowed lead resistance, specify the cable construction and record any intermediate connectors. Do not make a two-wire assembly a guaranteed three-wire 传感器 simply by adding a jumper at the receiving 仪表.
Four wires separate excitation from sensing
Analog Devices describes a four-wire arrangement using a current path and a separate voltage-sensing path to reduce lead-resistance influence. It requires a compatible input circuit. It does not remove every other error in a 温度 assembly. A four-core cable alone does not prove a four-wire measurement: confirm the 传感器 element connections, receiving terminals and configured wire mode together.
传感器 wiring and output-loop wiring are different
Keep two drawings in the job file: the 传感器-to-transmitter connection and the transmitter-to-控制器 connection. A quotation for a two-wire 4–20 mA transmitter describes an output and supply arrangement; it is not enough to choose an RTD 传感器's lead count. Similarly, an 仪表 with multiple terminals may use some for power or output. Ask the supplier to identify the function of each terminal on the actual version, rather than transferring a pin number from another model.
Verify the whole channel before relying on the reading
Prepare separate checks for the receiving electronics and for the installed 传感器 assembly. A resistance simulator checks the configured input and conversion path; it does not establish the installed probe's thermal response or the effect of its location. Record the simulator connection and leads with that check. Then document the 传感器 identification, installation and comparison method for the complete channel. Define acceptance requirements for the intended 温度 points rather than assuming a single wiring choice guarantees a system accuracy.
Apply this checklist to WESIVO 模块 inquiries
Published TT101 information confirms configurable RTD/thermocouple input and USB setup. TT248H information confirms Pt100 input and 4–20 mA with HART. Confirm the supported RTD wire modes for the exact ordered version; this article does not add an unverified four-wire capability. Send the 传感器 data sheet, number of leads, cable length and construction, terminal photograph, required range, output and certificate needs. Ask for the 传感器, input configuration and complete supply scope to be confirmed in the quotation.
先识别传感器，不靠端子数量判断
Pt100 表示在 0°C 时标称电阻为 100 Ω 的铂电阻传感器，并不规定引线数量。德州仪器（TI）的 RTD 指南介绍了这种传感器特性及不同接法。因此询价应同时说明传感器类型、线制及兼容的变送器输入。本文是通用技术说明，不表示每款 WESIVO 模块都支持全部线制。
两线测量包含引线路径
常规两线 RTD 接法中，测量电路看到的电阻包含传感器和两根引线。简单电路表达为 R测量 = R传感器 + R引线1 + R引线2。假设某传感器为 100 Ω，两根引线各贡献 1 Ω，电路看到的就是 102 Ω。该数值为假设电阻算例，不是 WESIVO 测试结果。将总电阻直接按传感器电阻换算，会产生温度偏移；增加显示位数不能消除引线贡献。
三线补偿取决于接线条件
DwyerOmega 介绍了三线补偿及引线电阻相近的假设。导体或连接电阻不一致，仍可能留下残余误差。采购时应索取变送器端子图和允许引线电阻，明确电缆结构，并记录中间接头。不能仅在接收仪表端加一根跳线，就把两线组件当作具有保证性能的三线传感器。
四线将激励与检测分开
Analog Devices 说明，四线接法使用电流路径和独立电压检测路径，以减小引线电阻影响，同时需要兼容的输入电路。它不能消除整套测温组件的所有其他误差。四芯电缆本身并不能证明使用了四线测量，应一起确认传感器元件接点、接收端子和设置的线制。
传感器接线与输出回路接线不同
在工单中分别保存传感器至变送器、变送器至控制器两张接线图。“两线制 4–20 mA 变送器”的报价描述了输出与供电方式，并不足以决定 RTD 引线数量。同样，多个端子可能部分用于供电或输出。要求供应商说明实际版本中每个端子的功能，不能照搬另一型号的针脚编号。
使用读数前核查完整通道
分别规划接收电子电路和已安装传感器组件的核查。电阻模拟器可以检查设置的输入及转换通道，却不能证明探头安装后的热响应或测点位置影响。将模拟器接法与引线记录在该项核查中，再保存完整通道的传感器标识、安装方式和比较方法。按实际温度点制定验收要求，不应假设某一种线制就保证整套系统准确度。
WESIVO 模块询价核对清单
已发布的 TT101 信息确认可配置 RTD、热电偶输入及 USB 设置；TT248H 信息确认 Pt100 输入和 4–20 mA 配 HART。具体订购版本支持的 RTD 线制仍需确认，本文不增加未经验证的四线能力。请提供传感器资料、引线数、电缆长度与结构、端子照片、所需量程、输出和证书需求，要求在报价中确认传感器、输入配置及完整供货范围。
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